@Zen09, they are Tombstoned (standing up, they were to ones on the circuit board) and the blue 30 awg wires soldered to the top pf them, bottom of picture. (sorry blurry picture, was using a friends crappy Sony camera and was in a hurry to finish in my 30 minute lunch hour.

Next I plan on making some low cost DIY sensors (voltage, current, tach), some info here.

I guess you mean sensors for Frsky system, when you ask low cost.
For now Frsky is the bottom as cheap telemetry, only GPS can be replaced cheaper.
Beware that not the sensors themselves will cost you to build, but also you must interface them to the receiver, what does the hub now, so a MCU is required.
If you want to DIY them just for hobby, and time has no much value for you, will be fun. Else, I doubt you will save something significant.

I guess you mean sensors for Frsky system, when you ask low cost.
For now Frsky is the bottom as cheap telemetry, only GPS can be replaced cheaper.
Beware that not the sensors themselves will cost you to build, but also you must interface them to the receiver, what does the hub now, so a MCU is required.
If you want to DIY them just for hobby, and time has no much value for you, will be fun. Else, I doubt you will save something significant.

Good point about the micro. Voltage, current, temp and tach and most other sensors can be feed into the analog ports and cost less than $2. The gps you have a good point about needing the micro interface. Also if you want or need more than 2 sensors, you need the hub interface and micro, thanks for your feedback!

There are many low cost IC's that are called "frequency to voltage converter"

It would not give a direct rpm number, but a voltage, this could be calibrated with a simple 10 turn trimmer pot to something like 100mV per 1,000 rpm. This would be easy to read the rpm straight from the voltage number. Using this example, 3.3 volts (maximum input for A1 and A2) would be 33,000 rpm, with a resolution of ~130 rpm.

Come to think of it, you could use a low cost hall sensor to measure current, like the low cost Allegro A1302 (~$1) to make a "current" (ammeter) sensor.

I use these in my home brew online racing wheel/pedals in iRacing, never worry about stupid (intermittent) pot failure as there is not pots to wear out or freeking glitch, see pictures).

Basically heat shrink a A1302 to the high current battery lead, maybe un-insulate the power wire where the hall sensor would touch (testing needed), then using a 10 turn trimmer pot to calibrate the output to something easy to convert, like 100mV per Amp. I have not tried this theory yet, maybe its not sensitive enough.

Can someone give me the link to the DIY low cost current sensor I read it a few days ago but I can't find it now, maybe a better solution than my , thanks!

Images

I'm installing a smartieboard too, would this stop me from just temporarily removing that board, doing this mod and then re-installing it or do I have to modify the smartieboard itself? I'm not even sure I need telemetry but if I do get it it would be nice to have it on the screen and not on some secondary display.

I saved myself the trouble and bought the telemetrez board from smartieparts. $30 shipped to my door, full functionality and 5 minutes with a drill and soldering iron (easy soldering nothing small) to avoid having to run any external wires with the DJT.

I saved myself the trouble and bought the telemetrez board from smartieparts. $30 shipped to my door, full functionality and 5 minutes with a drill and soldering iron (easy soldering nothing small) to avoid having to run any external wires with the DJT.

Yep full telemetry display. I can try to get pics later on, I opened up the DJT itself and drilled a hole in the side of it right above the circuit board. Cut the big black plug off the connector that comes in the TelemetrEZ board, stripped and soldered the wires to where they would go when plugged in as close to the base of the pins as possible. Then opened up one of the vents in the DJT bay on the radio big enough for the other end of the plug to go through and ran it through there.

I dunno I just was not about to pay for a "plug and play" easy board and have a hole in my radio with wires coming out. With that said, its still a better option, at least to me, than trying to solder onto small ass solder points.

Yep full telemetry display. I can try to get pics later on, I opened up the DJT itself and drilled a hole in the side of it right above the circuit board. Cut the big black plug off the connector that comes in the TelemetrEZ board, stripped and soldered the wires to where they would go when plugged in as close to the base of the pins as possible. Then opened up one of the vents in the DJT bay on the radio big enough for the other end of the plug to go through and ran it through there.

I dunno I just was not about to pay for a "plug and play" easy board and have a hole in my radio with wires coming out. With that said, its still a better option, at least to me, than trying to solder onto small ass solder points.

Nice, so what happens to this plug when you remove the DJT module and use another module (like SkyFly)? Where does this wires/connector go, can it fall back into the 9x or is it not removable or?

Mine is no longer removable unless I open the case. This is easily fixable by adding another plug inline which I might do but don't see the need in my case. Sticking with Frsky for the foreseeable future at least with this transmitter.

Oz, could you kindly upload a close-up picture of the diode you have added to the ppm? Though I can solder, am not a an expert at electronics. Don't want to commit a mistake while trying to use both modules. Thanks in advance. And thanks to renatoa for directing me to this thread